Dutasteride vs. Finasteride: Head-to-Head Clinical Trial Evidence

Dutasteride inhibits both type 1 and type 2 5α-reductase isoenzymes compared to finasteride’s selective type 2 inhibition, producing approximately 90–99% DHT suppression vs. ~70% for finasteride. This page reviews the head-to-head trial data comparing their clinical efficacy for androgenetic alopecia.

Key Trials

Study	Design	n	Duration	Outcome
Olsen EA, et al. 2006	Double-blind RCT; dutasteride 0.05, 0.1, 0.5, 2.5 mg vs. finasteride 1 mg vs. placebo	416	24 weeks	Dutasteride 0.5 mg and 2.5 mg produced significantly greater hair count increases than finasteride 1 mg; dutasteride 0.1 mg was comparable; dutasteride 0.5 mg was the approved dose in South Korea/Japan
Gubelin Harcha W, et al. 2014	Multicenter, double-blind RCT	917	24 weeks	Dutasteride 0.5 mg superior to finasteride 1 mg for total and target area hair count; statistically significant at 24 weeks

Pharmacological Context

Property	Finasteride 1 mg	Dutasteride 0.5 mg
Isoenzymes inhibited	Type 2 only	Type 1 + Type 2
Serum DHT reduction	~70%	~90–99%
FDA approval (AGA)	Yes (US)	No (approved in South Korea, Japan)
Half-life	~6–8 hours	~3–5 weeks

• Despite superior efficacy data, dutasteride is not FDA-approved for AGA in the US and is prescribed off-label
• The extremely long half-life of dutasteride (~5 weeks) has practical implications for dosing flexibility and side effect management

Full comparison: Finasteride vs. dutasteride

Sources

• Olsen EA, et al. “The importance of dual 5α-reductase inhibition in the treatment of male pattern hair loss: results of a randomized placebo-controlled study of dutasteride versus finasteride.” J Am Acad Dermatol. 2006;55(6):1014–1023.
• Gubelin Harcha W, et al. “A randomized, active- and placebo-controlled study of the efficacy and safety of different doses of dutasteride versus placebo and finasteride in the treatment of male subjects with androgenetic alopecia.” J Am Acad Dermatol. 2014;70(3):489–498.